NEIEP Machine Room Maintenance (550) Practice Test

When you find metal debris in gearcase oil, the type of metal often points to which parts are wearing. Bronze fillings mean bronze components are wearing, and in a gearcase those are typically bronze gears and bronze bearings or bushings. Bronze is used for those parts because of its anti-wearing properties and compatibility with metal-to-metal contact in the geartrain. If the crankshaft were wearing, you’d expect ferrous (steel) particles to show up in the oil, not bronze. Seals wearing would shed material from elastomers, not bronze, and piston rings wear would generally produce iron or steel particles from the rings and cylinder surfaces. So bronze filings in the oil most strongly indicate wear of bronze gears and bearings.